Calculating Solana notification latency

Long story short, there is no 100% accurate way to calculate solana notification latency regardless of who you get your data from. For anyone that tells you otherwise, you should seek to validate the information yourself.

The reason calculating latency is difficult is because solana doesnt store milliseconds in its blockchain timestamps.

Solana produces about 2 to 3 blocks a second. If the time between blocks was constant, we might be able to estimate the milliseconds of the block but a slot is not always occupied by a block or sometimes it takes longer to validate a block. For this reason we dont know for sure how many blocks will be created each second.

If solana creates a block at 9:00am and 0 milliseconds, we might receive the notification 100ms later at 9:00am and 100ms. We can then calculate the latency by:

In this case our latency value of 100 milliseconds is correct.

However, if solana created a block at 9:00am and 800ms and we receive the notification 150ms later at 9:00am and 950ms, the timestamp we would receive from solana would still be 9:00am and 0ms as solana doesnt pass on or store the millisecond information. In this case, our calculation becomes

9:00am and 950ms is the current timestamp at the point of receiving, 9:00am and 0ms is the solana timestamp passed on. We get a result of 950 milliseconds latency which is incorrect. The real latency is 150ms which can be correctly calculated if we had the original block time with milliseconds which was 9:00am and 800ms.

What can we do about this?

Whilst its not possible to calculate latency on an individual level, we can calculate the average latency. Since the maximum error in latency is 1 second, we can subtract 500ms from the average. This will give us a better idea of the average latency.